The breaking point to wich the lines of friendship and romance in a relationship between two people are blurred to complete utter confusion resulting in frustration, IE: vague text replys, mixed signals, and lack of acknowledgment for the other person on an affectionate level. This is usually in the case of having a crush on an individual who's ambiguous responses leave the other individual riddled with hormonal rage till they flip either their shit or dignity to somehow save face before falling victim to the friend zone, thus leading to a climax of arguing, interrogation or abandonment of an ambiguous crush, thus cracking under pressure.

John: hey how's that thing going with Sally?

James: I just flipped shit and told her to stop leading me on, she wasn't being direct enough, I didn't know if she really liked me back